Mobile devices, for example mobile phones, mobile music players like MP3 players, and mobile navigation systems are very popular and commonly used in all kinds of environments, for example in enclosed environments like in a car or in a room of a building or in outside environments. Furthermore, audio reproduction of audio data of the mobile device is commonly performed by earspeakers or headphones. However, when audio data is reproduced by earspeakers or headphones, this audio reproduction appears to the user as if the user would be in an acoustically dead room, a so called anechoic room. Therefore, some mobile devices provide special acoustic filters simulating a certain environment, for example or a church or a stadium. However, commonly this does not match appropriately to the environment where the user stays and therefore there is a mismatch between the acoustic sound and the optic environment experienced by the user.
Another popular feature of mobile devices is the ability to determinate a current position of the mobile device. This ability may be used for navigating or guiding a user in unknown environments. However, in enclosed environments, for example in buildings, satellite signals for determining the position cannot be received always properly and thus a determination of the position in such enclosed environments is not possible. To overcome this problem, some mobile devices include acceleration sensors to determine relative movements of the mobile device and thus to determine a global position. However, these acceleration sensors add additional costs to the mobile device and do not provide accurate positioning information especially when the mobile device experiences a lot of movements in various directions.
Therefore, it is an object of the present invention to overcome the above-described problems by providing a user of headphones improved audio data and by providing an improved position determination for a mobile device. As will be seen from the following summary of the invention, for solving these problems a common underlying problem has to be solved namely an appropriate method for determining an acoustic property of an environment.